After four hours of watching, approximately 4,000 spectators reluctantly left Falls Church high school's Webber Stadium near midnight last Saturday. They would have stayed longer had there been more to see.

No, it wasn't an extra long football game. For most, it was something more exciting than that.

It was the first annual Falls Church tournament of Marching Bands, featuring 12 high school marching bands and the United States Marine Drum and Bugle Corps. All of the high school bands, except for host Falls Church, competed for tournament awards.

If Northern Virginia has ever witnessed as grand an exhibition in the past, no one could recall it. Indeed, it would be hard to imagine.

Four local bands performed - Falls Church, Madison, Jefferson and T. C. Williams. Four bands came from other parts of Virginia - Princess Anne of Virginia Beach George Washington of Danville, E.C. Glass of Lynchburg and J. R. Tucker of Richmond. From out of state there were Fairmont of Fairmont, W. Va., West Genessee of Camillus, N.Y., Sylva Webster of Sylva, N.C., and Statesville of Statesville, N.C.

There were spinning rifles, flaming batons, cannon shots, trains with smokestacks puffing, swords, flags, can-cans, poms-pons, bagpipes and seven different variations on the Star Wars theme. And much more.

Anyone who went to the tournament with the impression that "if you've seen one marching band, you've seen them all" was quickly proved wrong.

Falls Church opened the show with an impressive, precise performance. In fact, one of the tournament's 10 judges, Ray Cox, a band director in Indiana, said three-quarters of the way through the night, "The level of competition here is very high. There's not a poor band here. They may not all be at the Falls Church level, but they're all exceptional."

By the time the third band of the night - Princess Anne's marching Cavaliers and "The Red Machine" (a special dance ensemble) - marched onto the field, the crowd was beginning to realize how varied marching bands could be. Princess Anne, which had five first place finishes in various competions in 1976, and last spring retired the prestigious Apple Blossom Queen's cup in Winchester, Va., entered the field 180-strong.

Princess Anne set the tone for the other "show-biz" marching bands that were to follow. Some of its members danced, some marched, and many played. They performed fragments of a spirited Spanish march, and then, after a quick maneuver or two, they were marching majestically to Indian music.

But Princess Anne wasn't even amont the top three finalists on that crisp autumn night.

West Genessee, the night's fifth band, with the help of 550 supporters who traveled from near Syracuse, N.Y., for the performance, took Princess Anne's fine show several steps further.

Dressed in shiny blue-and-gold uniforms, West Genessee marched to complex, non-traditional marching music, and they made formations as complex as their music. No "Stars and Stripes" for them. But they made the difficult look easy, and they finished their performance waving flags and streamers with incredible precision while the band played on.

Off the field, the West Genessee band members hugged and kissed, and some even cried. "It was a tremendous performance," director Bruce Burritt told them emotionally.

West Genessee had left young and old alike walking with a bounce in their step. "When you see a band like that, it's hard to believe they're just kids," said one spectator.

If West Genessee had heated up the crowd, two bands later E. C. Glass played up to it with a dramatic showy performance which included a brief pantomime skit at the beginning, a cancan routine in the middle and a spirited double flag waving finale.

Later the Sylva Webster Golden Eagles took the field, and from the start it was clear that the small mountain school band was, in the words of its director, Stephen Trull, "into hype."

Sylva Webster was loud, brassy and precise. They began by twirling rifles briskly into the air and catching them. No one missed. They strutted smartly, always facing the judges. A small group of supporters whooped while they played. The only sour note, literally, came when a trumphet soloist garbled a passage.

The final high school band of the evening was also the most unique. There was no hype for the Statesville Grenadiers. Dressed in Scottish military attire, they featured a large section of bagpipers and perhaps the evening's most traditional marching performance.

While judges tallied their scores, the sound of the United States Marine Drum and Bugle Corps filled the stadium and tumbled into the surrounding community. They played some "hype" numbers, including a salute to Louie Armstrong which had some members of the crowd shouting, "God ahead!" and "Louie would love ya!"

But it was the "Battle Hymn of the Republic" that brought the crowd to its feet.

"Just when you think they can't possibly sound any better," someone said of the Marines, "they do."

The judges awarded first place to early favorite West Genessee with Sylva Webster second and Statesville third.

"Man, we are thrilled," said West Genessee's Burritt, clutching the first place plaque. "I was really worried when Sylva got through. There were so many great bands here. I mean, there were some really tough bands tonight."

But for many in the crowd, there could have been even more.